Control system for an electrically propelled traction vehicle

ABSTRACT

A control system for an electrical propulsion system for a large wheeled vehicle adapted to haul a payload, the vehicle having an internal combustion engine and an electric generating means driven by the engine. The control system measures selected parameters and controls the engine and generating means to maximize output, and records historical operating data relating to the vehicle and its systems, and has a 2 digit display that provides information useful in troubleshooting problems.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.07/860,786, filed Mar. 31, 1992, now U.S. Pat. No. 5,280,223.

BACKGROUND OF THE INVENTION

The present invention generally relates to electric propulsion systemsfor traction vehicles, and more particularly, to a control system forsuch an electric propulsion system.

An electric propulsion system for a traction vehicle, such as a largehaulage truck, often comprises a prime mover-driven electric generatingmeans which supplies electric power to a pair of high horsepowerelectric traction motors that are respectively connected in drivingrelation to a pair of wheels located on opposite sides of the vehicle.The prime mover is generally a relatively large diesel engine and thetraction motors are generally adjustable speed reversible direct current(d-c) electric motors. The operator of the vehicle controls the speedand direction of travel of the vehicle by manipulating one or more speedcontrol pedals and a forward-reverse-neutral selector switch. Anaccelerator speed control pedal is adapted to control the diesel enginespeed which determines the power output of the generating means tothereby vary the magnitude of the voltage applied to the tractionmotors.

A moving vehicle is decelerated by releasing the speed control pedal andeither allowing the vehicle to coast or activating its mechanical orelectrical braking system. In the electrical braking mode of operation,the motors function as generators and the magnitude of the voltagegenerated across the armature windings of each motor is proportional tothe rotational speed and the field excitement current of the motor.Dynamic braking resistor grids are connected across the armatures of therespective motors to dissipate the electric power output of the motorsduring such electrical braking. The average magnitude of current in eachresistor grid is a measure of the braking effect of the associatedmotor.

Such vehicles are most often employed in off the road environments, suchas strip mines and the like which have terrain grades that can besevere, given the fact that the vehicles carry extremely large payloads.For obvious reasons, it is common to establish a maximum allowablepropulsion speed for the vehicles and it has been conventional practiceto include a preset overspeed limit in the controls of the propulsionsystem.

Several factors affect the selection of the speed limit. It cannot behigher than the maximum safe speed for entering any downhill grade ofthe roadway along which the vehicle will travel. The maximum safe entryspeed is the highest constant speed that can be maintained on thedownhill grade with the electrical retarding in effect. If the actualentry speed were higher than the maximum, the available dynamicretarding effort of the traction motors would be insufficient to keepthe vehicle from accelerating into a runaway condition. The maximumretarding ability of d-c traction motors depends primarily on thecommutation limit of the motors. Above the commutation limit, electricalarcs or sparks can occur with resulting damage to the motor commutatorand brushes. The commutation limit is a function of the armature currentmagnitude multiplied by the armature velocity. At high speeds thecurrent must be kept relatively low in order to avoid such arcing,thereby resulting in lower available dynamic retarding effect. If theavailable retarding effect were insufficient to slow the vehicle,service brakes could be used. However, at speeds above about 5 miles perhour, service brakes should not be used because such brakes rapidly wearat such speeds.

Even though the payloads carried by such vehicles is extremely large, itis desirable in terms of efficiency to have the vehicles travel as fastas is safely possible. When the vehicles are moving up a relativelysteep grade, the maximum capacity of the diesel engine and the electricgenerating means is desirably used. This insures that the maximum speedis achieved.

Because of the expense of acquiring and maintaining such vehicles issubstantial, it is also highly desirable to maximize the productivity ofsuch vehicles and it is therefore desirable to have data relating to itshistory of operation of the vehicle to assist the owner-operator inevaluating the operation of the vehicles and to aid in the maintenanceof them. Additionally, if a malfunction occurs in the operation of thevehicle, it is desirable to be able to troubleshoot the problem andperform corrective maintenance as well as preventative maintenance ofthe vehicle.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide animproved control system for an electric propulsion system for tractionvehicles, which has unique features and capabilities which contribute toreduced manufacturing costs, as well as reduced maintenance costs, byvirtue of the control system having the capability of acquiringinformation and data which facilitates troubleshooting and maintenanceoperations.

Another general object of the present invention is to provide such animproved control system, which by virtue of its improved design,controls the electric propulsion in a manner which maximizes the outputof the prime mover-driven electric propulsion system.

Still another general object of the present invention is to provide suchan improved control system which uses measured parameters in such a wayto increase the output of the electric generating means of the electricpropulsion system in a manner which does not substantially increase therisk of damage to the electric generating means by operating abovecontinuous rating limits.

Another object of the present invention is to provide an improvedcontrol system which automatically controls the diesel engine andelectric generating means in a manner which automatically utilizes themaximum horsepower capacity of the diesel engine at any given time whenmaximum horsepower can be desirably utilized.

Yet another object of the present invention is to provide such animproved control system which includes processing means and memory meansin which historical operating and status data can be stored for thepurpose of providing reports relating to the operation of the vehicle,

Still another object of the present invention lies in the provision ofproviding historical data relating to the operation of the vehicle whichcan be extremely useful in evaluating the productivity of the vehicle aswell as detecting improper operation and perhaps abuse of the vehicle bya driver.

Another object of the present invention is to provide such an improvedcontrol system which records in the memory means of the processing meansspecific information relating to the electrical parameters of theelectric propulsion system and mechanical parameters of the vehicle anddiesel engine in a manner whereby time logs of various types ofoperating conditions are maintained. A related object lies in theprovision of having reports relating to such time logs generated on adaily basis, as well as for the two preceding three month periods.

Still another object of the present invention is to provide such animproved control system which includes a display means which can belocated in the cabin of the vehicle and which provides a visual read-outof various status conditions of the vehicle, the electrical generatingmeans as well as the diesel engine.

A more specific object lies in the provision of having a plurality oftwo digit codes which identify specific status conditions, includingfault conditions, relating to the operation of the diesel engine, theelectric generating means and the vehicle.

Other objects and advantages of the present invention will becomeapparent upon reading the following detailed description, whilereferring to the attached drawings, in which:

FIG. 1 is a functional block diagram of an exemplary control system forthe electric propulsion system for an electric traction vehicle;

FIG. 2 is a graph of alternator current versus voltage and particularlyillustrating the operation of the thermal simulator feature of thepresent invention;

FIG. 3 is a graph illustrating the prime mover or engine speed versuselectrical load on the engine and particularly illustrating theautomatic loading feature of the present invention;

FIG. 4 is a front view of the display panel of the present invention;and

FIG. 5 is an electrical schematic diagram of the display illustrated inFIG. 4.

DETAILED DESCRIPTION

Broadly stated, the present invention is directed to a control systemfor an electric propulsion system for an electrically propelled tractionvehicle such as a large off-highway haulage truck. The control systemincludes a central processing unit with associated memory coupled withanalog input and output boards, as well as digital input and outputboards for receiving signals that are indicative of various operatingconditions of the electrical propulsion system and for transmittingcontrol signals thereto. The control system has significant andsubstantial control capabilities compared to prior control systemscomprised essentially of hardwired circuits.

Among the considerable features and advantages of the control systemembodying the present invention, is the capability of operating theprime mover, preferably a diesel engine, and the electric generatingmeans, preferably an alternator, in a manner whereby optimum horsepoweroutput is produced. This results in the vehicle having the capability ofoperating at optimum efficiency consistent with temperature and otherconstraints and increases the productivity of the vehicle. Moreover, thecontrol system has the capability of maintaining records relating to theoperation of the diesel engine, the alternator and the vehicle forrecording operating times which are useful in determining theproductivity of the vehicle and for both preventative and correctivemaintenance programs.

The data that is maintained is adapted to provide a number of quarterlyreports as well as daily reports for use by the owner/operator of thevehicle. Moreover, such recorded information is also useful indetermining whether drivers of the vehicle are negligently operating thevehicle or even abusing the same and enables the owner/operator to takecorrective action if the data indicates that it is needed. The controlsystem has a display which is extremely useful in performingtroubleshooting, and status conditions are displayed in the form oftwo-digit codes which in many cases identifies a fault condition. Use ofthe displayed code in combination with a manual can often quickly revealthe cause of the fault condition.

Turning now to the drawings, an exemplary electric propulsion system isshown in FIG. 1, together with the control system indicated generally at10. The vehicle includes driver controls located within the box 12 andincludes an accelerator pedal 14, a retard pedal 16 and aforward-neutral-reverse selection switch 18. The accelerator pedal 14 isconnected to an engine control means 20 which controls the speed ofoperation of a diesel engine 22.

The accelerator pedal 14 is adapted to be depressed by the driver and atleast partially controls the engine control module 20 and also sendssignals to the controller 10. At zero pedal depression, the engineoperates at its low idle speed of approximately 750 rpm. At maximumpedal depression, the engine will be operating at preferably 1900 rpm.When the pedal is initially depressed, a digital signal identified as"AS" is sent to the control system 10 causing it to set up in thepropulsion mode. This pedal also sends an analog signal proportional toits depression to the engine control module 20 that varies the speed ofthe engine from 750 to 900 rpm. The control system 10 is also adapted toapply either a high or low idle speed from the control system 10 inaddition to the variable speed provided by the pedal 14.

The retard pedal 16 is a separate pedal from the accelerator pedal andwhen the driver pushes this pedal, the system is placed in the retard orelectrical braking mode. When the pedal is depressed, a digital signalcalled RS is sent to the control system 10 causing it to set up in theretard mode. The engine will then be caused to operate in the high idlespeed of approximately 1650 rpm whenever this pedal is depressed. Anoutput from the control system to the engine control module 20establishes this condition. An analog signal called "retard in" is alsosupplied from this pedal to the control system 10 and its value isproportional to the amount the pedal is depressed.

The selector switch 18 is used by the driver to select either theforward, neutral or reverse conditions. The control system 10 thenchanges the direction of current flow in the motor field windings of themotors 28 and 30 and thereby specifies the direction of rotation of themotors and therefore the direction in which the truck is moved.

The output shaft of the diesel engine 22 is drivingly coupled to therotor of an alternating current (a-c) generator 24, hereinafter referredto as an alternator, which has a set of 3-phase main windings (notshown), a pair of auxiliary or tertiary windings (not shown), and fieldwinding 26. The 3-phase generally sinusoidal alternating voltage that isgenerated in the main windings of the alternator 24 is converted todirect voltage by means of a rectifier diode panel 27.

The diesel engine-driven alternator 24 serves as a source ofenergization for a pair of adjustable speed d-c traction motors 28 and30, whose respective armature windings are connected via lines 32, 34and 36, in series with one another between the output terminals of therectifier diode panel 27. The motors 28 and 30 have separately excitedfield windings 38 and 40, respectively. The rotors of these motors arerespectively coupled through the suitable speed reduction gearing to apair of wheels (not shown) located on opposite sides of the vehicle. Bysuitably controlling the speed of the engine 22 and the excitation ofthe alternator and motor fields, the vehicle can be propelled (alsoknown as "motoring") or dynamically retarded (also known as "electricalbraking") by its motors in either a forward or reverse direction.

Each of the motors 28 and 30 have an associated speed sensor 54 which ispreferably a reluctance type magnetic sensor that measures the armaturespeed by counting gear teeth on the armature shaft. The speed feedbackis applied to the analog input/output board 50 of the control system 10.The speed sensor is used by the control system 10 to control the retardspeed control function, the speed override and overspeed function, thecontrol of the park brake and the control of the reverser as well asother functional operations.

During the motoring mode of operation, the motors 28 and 30 will eachrotate at a speed that depends on both the magnitude of excitationcurrent in the fields 38 and 40 and the magnitude of the voltage appliedto the respective armature windings. The latter magnitude is a functionof both the speed at which the alternator 24 is driven and the magnitudeof the excitation current in the alternator field winding 26. Thealternator field excitation current is supplied to an alternator fieldwinding 26 by the auxiliary winding (not shown) of the alternator 24 byan alternator field static exciter panel 42. This panel controls theamount of excitation current supplied to the alternator field inresponse to an analog signal on line 44 that is generated by the controlsystem 10. The panel comprises diodes and silicon controlled rectifiers(SCR's). The power for this panel is supplied by an auxiliary windingcalled a tertiary winding located in the alternator and is not shown inFIG. 1.

The alternating field is a rotor winding of the alternator and theamount of d-c excitation current applied to this winding controls theamount of voltage and current that are produced on the main 3-phaseoutput. By controlling the I_(AF), the amount of electrical powerapplied to the motors can be varied from zero to maximum. This currentis applied through slip rings (not shown) since this winding is rotatingat engine speed. A shunt 46 provides a I_(AF) feedback signal that isprovided to the control system 10 during operation. The shunt 46 ispreferably a 400 amp. 100 millivolts shunt.

The motors 28 and 30 are often referred to in the art as motorizedwheels and comprise a d-c motor, gear box and vehicle rear axle that isintegrated into a single package called a motorized wheel. The motorizedwheel is bolted to the rear axle box structure of the truck. Rims anddual tires are attached to each motorized wheel and the armature shaftis coupled to the tire through the compound gear reduction mechanism.Service brakes and park brakes are generally supplied and act on themotor armature shaft on certain trucks. The control system 10 iscomprised of a CPU 48 having associated memory, as well as an analoginput/output board 50 and one or more digital input/output boards 52.The analog input/output board 50 preferably includes counters whicheffectively convert selected speed related analog pulses to a digitalvalue which can be processed by the CPU 48. The CPU is preferably aModel 80960KB microprocessor integrated circuit manufactured by IntelCorporation and the associated memory preferably comprises a 1 megabytememory in which the program resides.

The speed of the diesel engine 22 is also sensed by an engine speedsensor 56 which is preferably a reluctance type magnetic sensor thatmeasures the speed/engine/alternator speed by counting gear teeth on agear in the alternator 24 and this signal is also applied to the analoginput/output module 50.

The current supplied to the motor fields 38 and 40 originate from amotor field static exciter 60 which is connected to a reverser 62 thatcontrols the direction of current that is applied to the motor fieldwindings. The motor field static exciter is a solid-state phasecontrolled bridge that utilizes diodes and SCR's to vary the amount ofcurrent supplied to the motor fields as determined by motor fieldcommands provided by the analog input/output module 50 and whichoriginate from the central processing unit 48. The reverser 62 is abi-stable switch that reverses the direction of current flow through themotor fields and thereby controls the direction in which the vehiclewill move. The reverser 62 is controlled by the CPU 48 via the digitalinput/output module 52.

A motor field contactor 64 is provided and this contactor sets up thefield circuit which allows current to flow from the motor field staticexciter 60. The contactor 64 is closed in the propulsion and retardingmodes of operation, but is open in the neutral mode. It is controlled bythe CPU 48 via the digital input/output module 52. A shunt 66,preferably a 400 amp. 100 millivolts shunt, provides the I_(MF) feedbacksignal that is indicative of the motor field current and the signal isapplied to the analog input/output module 50. Each of the motors 28 and30 has respective shunts 68 and 70 which are preferably 1000 amp. 100millivolts shunts that provide a signal that is indicative of the motorcurrent in the respective motors and this signal is applied to theanalog input/output module 50.

A voltage sensor 72 is provided in line 32 to measure the output voltageof the rectifier diode panel 27 and contactors 74 and 76 are alsoprovided and are closed in the propulsion mode and opened in theretarding mode. Each of these contactors, as well as all othercontactors in FIG. 1, also has a position sensor that gives a digitalfeedback to the control system 10 to indicate whether it is opened orclosed.

When the control system 10 places the vehicle in the retard mode, thecontactors 74 and 76 are opened and the motors 28 and 30 function asgenerators. When this is done, resistance grids 76 and 78, which arehigh power banks of forced air cool resistors used to dissipate theenergy created by the motors acting as generators in the retarding mode,are placed in circuit by the contactors 80 and 82. When the vehicle isin the retarding mode, the contactors 80 and 82 are closed, but areopened in the propulsion mode. The resistor grid is preferably comprisedof 4 to 10 resistors and additional contactors 84, 86 and 88, which arecontrolled by the CPU 48 via the digital input/output module 52 andwhich are controlled to close at unique values motor speed.

These latter contactors provide extended range retardation and functionto reduce the value of the resistance in the resistor grids 76 and 78down to low vehicle speeds. As the vehicle and motors slow, the amountof voltage produced by the motors acting as generators falls andtherefore the same level of retarding current must be maintained byreducing the resistance of the load. The control of the contactors issuch that they are sequentially closed as a function of the motor speed.Additional contactors may be provided in addition to the threecontactors 84, 86 and 88.

A display 90 is also connected to the digital input/output module 52 andit provides information relating to the status of the operation of thevehicle and of the control system 10.

In accordance with an important aspect of the present invention, thereare times during the operation of the vehicle where increased truckperformance is very desirable, such as traversing a relatively steepgrade for a relatively short time. During operation, an electric drivevehicle can only utilize the full horsepower available from the engineover a limited range that is commonly referred to as the constanthorsepower region. Referring to FIG. 2, there is a graph of thealternator output amp versus the alternator output voltage and aconstant horsepower curve is shown and identified. As the vehicleaccelerates from a stop toward full speed, the voltage produced by thealternator increases. To make this voltage increase, the current appliedto the alternator rotor (I_(AF)) must also increase. In prior artvehicles, the control system has generally been operated to allow I_(AF)to increase to its continuous rating, shown to be 220 amps in FIG. 2,which is the maximum value of I_(AF) that can be applied continuouslywithout exceeding the rotor temperature limit as determined by the typeof insulation used in the rotor and other factors. This point is calledthe upper corner point in the art and the electrical system can nolonger continue to increase the alternator voltage and remain on theconstant horsepower curve.

In operation, the voltage limit control of such prior control systemscauses the output voltage to follow from points A to C, with the lattermove resulting in the full engine horsepower not being utilized becausepoint C is not on the constant horsepower curve. It is also well knownthat alternators have a short time rating during which operation can becarried out above the continuous rating for a short period of time. Byutilization of the alternator short time ratings as described in thisinvention, the voltage can follow the points A to B which utilize fullengine horsepower up to 2000 V d-c. The amount of time is inherently afunction of the operating conditions and the load being placed on thealternator, as well as heat transfer and storage characteristics of thealternator, the electrical resistance of the rotor and the operatingspeed of the engine.

The important consideration is the temperature of the rotor of thealternator, and it should be readily appreciated that when thealternator is operated in the short time rating, the temperature of therotor will necessarily increase. As should also be readily understood,the alternator cannot operate indefinitely in the short time rating orthe rotor will become overheated and damage would inevitably result.

In accordance with an important aspect of the present invention, thecontrol system utilizes known characteristics and measured electricalparameters to estimate the rotor temperature, since it cannot beeffectively directly measured, by running a computer simulation of therotor temperature which is calculated at predetermined time intervals,such as preferably every five seconds. The computer simulation takesinto consideration the surface heat transfer coefficient of thealternator which is a function of the engine speed. Thus, differentcoefficient values are preferably used including values corresponding tothe rated engine speed, the high idle speed and the low idle speed. Theheat storage capacity of the alternator is a value that is availableempirically as is the resistance of the rotor at a particulartemperature. Using this data plus the ambient temperature and thecurrent flowing through the rotor, the temperature rise of thealternator can be accurately simulated and the control system operatesto have the alternator run in the short time rating until thetemperature reaches a predetermined maximum temperature. At that point,the control system reduces the alternator to its continuous ratingvalue.

The temperature rise of the rotor is calculated based upon the followingfinite difference equation: ##EQU1## where T=temperature rise of rotor(°C.),

Δt=Time step,

H=Surface heat transfer coefficient (Watts/C),

C=Heat storage capacity (watt-sec-/°C.),

R=Resistance of rotor (ohms),

I=RMS amps during Δt, and

T_(amb) =Ambient temperature (°C.).

Utilizing this implemented equation, when the temperature rise plus theambient temperature is reached, preferably at a value of approximately220° C., the control system will reduce the current from the short termrating to the continuous rating.

In accordance with another important aspect of the present invention, itis important to utilize the full horsepower capacity of the dieselengine to maximize production for reasons that have been hereinbeforedescribed. Prior control systems have typically utilized a maximumhorsepower rating for an engine which is set in the control system andwhich is not exceeded under any conditions.

Referring to FIG. 3, there is a graph of engine speed versus electricalload on the engine and this graph is generated by measuring theelectrical load presented by the alternator on the engine as a functionof the engine rpm as measured by the speed sensor 56 of FIG. 1. Thegraph is developed to optimize the criteria of the engine capability asa function of rpm, the driver acceptability as it relates to thedriver's ability to control the vehicle under all modes of operation andthe best utilization of fuel. Prior control systems typically have had amanual mode of HP loading, where the vehicle is put into a self-load ora load box mode. The braking resistor grids 76 and 78 are reconnected tothe output of the alternator and used to load the engine while the truckis stationary. The procedure results in a fixed value which is stored inthe control and is thereafter used, and is identified as point A on thegraph shown in FIG. 3.

However, in accordance with the important aspect of the presentinvention, the control system can also operate in an automatic modewhich operates to increase the load on the engine thereby producingadditional horsepower until the diesel engine speed starts to fall belowits rated full load speed. By doing this, the maximum amount ofhorsepower that the engine can deliver is used. While each engine has arated horsepower, it is typical for the horsepower to be plus or minusfive percent from the rating under favorable temperature and altitudeconditions. Under unfavorable conditions, such as high altitude or dirtyfuel filters and the like, the engine may not be capable or producingthe rated horsepower. When the control system operates in the automaticloading feature, the vehicle will be taking advantage of whatever thecapacity of the engine is at a particular point in time and may have theeffect of making the vehicle more productive by increasing the truckspeed on uphill grades if the engine has additional capacity forexample. The automatic mode is relatively easily implemented, andrequires only the engine speed signal from the speed sensor 56 as aninput signal to the central processing means. When the speed falls belowa predetermined value, the processing means reduces the alternator loadbeing applied to the diesel engine.

In accordance with yet another important aspect of the presentinvention, the central processing unit 48, together with its associatedmemory, are adapted to receive the various signals relating to theoperation of the diesel engine 22, the alternator 24 and the vehicleitself, and this information is selectively stored in the memory andprovides a database of information which can be used to generate reportsthat are extremely useful for management and maintenance people inmonitoring the operation of the truck.

Such statistical data reports can be advantageously used to determinetruck productivity and can therefore determine what percentage of thetime the vehicle is doing useful work. Also, the statistical data candetermine the severity of duty of the vehicle, since horsepower, amperesand motor temperatures are measured and from that the determination ofthe severity of the duty cycle of the vehicle can be made. This wouldenable management of a mine, for example, to gather information forfuture planning, i.e., whether a larger diesel engine may be required ora different gear ratio needed to optimize performance.

Such statistical data also can be helpful in administering warrantyrequirements may enable the manufacturer to determine whether acomponent failure was the result of a manufacturing defect, driver abuseor poor maintenance. Additionally, preventive maintenance can be morereliably scheduled depending upon the duty cycle or changes in the dutycycle of the vehicle. For example, if the rate of logged mileage on thevehicle changes drastically, the oil change interval might beaccordingly changed. If the average motor temperature increases, it maybe desirable to check the cooling blower and air ducts for possibledamage. Additionally, abnormal operating conditions, such as driving thevehicle with the brakes applied, or an excessive number of vehicleoverspeeds and the like, is readily discoverable with the data that ismaintained. Finally, a historical record for each vehicle can bemaintained.

The central processing unit 48 stores the received data in queues thatare preferably periodically reset according to unique rules. Among thequeues are a lifetime queue which is not automatically reset so thatdata collected from the time the system is started until a manual resetis invoked is maintained. This queue provides a life history of eachvehicle. A second queue is a this day queue which is automatically resetat the end of each day. It gives a daily history of what happened to thevehicle during the day. Another queue is a this quarter queue which isreset at the end of each three month period and gives a quarterlyhistory which must be read before the end of the quarter. The centralprocessing unit also maintains in its memory a last quarter queue whichis reset at the start of a new quarter. It shows what took place duringthe previous quarter. Finally, certain statistical data is maintained ina manufacturer queue which contains two lifetime queues that have beendescribed, and this is preferably capable of only being read or reset bymanufacturing personnel. The report is tied to a particular vehicle withparticular components. The serial numbers of the vehicle, the dieselengine, motors, alternator, etc. are given in the report. The lapsedtime that the report covers from start date to finish date are alsogiven.

More specifically, the statistical data that is recorded includesoperating hour monitoring of the diesel engine 22, the motors 28 and 30,the alternator 24, the propulsion mode, retarding mode, coast mode, idlemode, fault down time and the total truck. Parameter counters recordevents, including some which are time stamped and such events includethose of overspeed, dump body switch operation, dump body overrideswitch operation, service brake application, body load switch operation,selector switch operation above three miles per hour, engine started,accelerator pedal 14 and service brake pushed at the same time, theaccelerator pedal and park brake applied at the same time, retard switch16 and service brake pushed at the same time, the speed being greaterthan 0.3 mph and the part brake applied, speed override and reverser 62operation. Other events also include the two digit display 90 resetpushed, the accelerator pedal 14 and retarding pedal 16 pushed at thesame time, the selector switch being changed, the vehicle operating modebeing changed among the propulsion, retarding and coast modes, thepick-up and drop-out of various contactors, the accelerator pedal 14being pushed with the motor temperature above 220° C. and the retardpedal 16 being pushed at zero speed. While other events may be recorded,the above described events are representative of the kinds of eventsthat are preferably recorded in memory.

Moreover, parameter profiles are maintained which include the propulsionand retarding mode of operation, the motors 28 and 30 armature currentsand temperatures and motor field current, as are the net inputhorsepower, the engine speed, the vehicle speed and the distancetraveled.

All of this information can be used for preparing extremelycomprehensive statistical data reports that can be used by managementand/or maintenance personnel.

In accordance with yet another aspect of the present invention, and aspreviously mentioned, the system includes the display 90 shown in FIG.1, which is also illustrated in detail in FIGS. 4 and 5. The display 90has a two digit display readout 92 which provides diagnostic informationto the driver of the vehicle and the display panel also includes up anddown search buttons 94 and 96, respectively, as well as a reset button98. LED indicators 100 and 102 are also provided to indicate the firstand last display codes that are current. The reset switch 98 also has anassociated LED 104. The display 90 provides a two digit display whichidentifies various problems by a fault code number. If a problem arises,there may be a number of faults that result, in which case, severalcodes may be generated. By using the search buttons 94 and 96, thesecodes may be viewed by scrolling through the active codes. Dependingupon the particular fault, the code may be maintained for a preselectedtime period after it occurs.

In a preferred embodiment of the present invention, associated with eachcode on the two digit display provided by display 90 is a shortdescription of troubleshooting techniques. This description or help textis activated using a portable test unit (PTU), such as a laptop orportable computer, to view event data saved when the respective codesoccur. For example, the F1 function key on a keyboard provides help onany screen in the PTU. While the PTU is being used to view event data,the F1 key activates the troubleshooting help text for the two digitdisplay code. Thus, whatever the event code, use of the F1 key brings upthe appropriate troubleshooting help screen. These context sensitivehelp screens allow the operator to apply troubleshooting techniquesspecifically directed to the event data. In addition, an on-lineglossary can be provided to help the troubleshooter understand the termson the screen.

Alternatively, a troubleshooting guide which described all fault codesmay be provided, along with a chart which gives a brief explanation ofthe codes and possible causes of the faults. A description of thevarious two digit display panel codes are set forth in Appendix A whichis attached hereto. Each code identifies the condition associated withthe code number, and an indication of the possible cause, and the timeperiod for which the code is maintained.

As an additional troubleshooting aid in a preferred embodiment of thepresent invention, two PTU screens illustrating the necessary signals toachieve acceleration and retard sequence, respectively, may be created.These screens contain ladder diagrams which use backlighting to enablerepair personnel to determine which signal is preventing the controlsystem from achieving the accel or retard state, and the correspondingcontactor sequence. The logic diagrams preferably include operatorinputs as well as propulsion system feedbacks. Because the logic screensrun in "real-time", as a signal is fixed, the logic screen display isupdated. This updating allows the troubleshooter to test grounding orpowering points in the signal paths and immediately determine whetherthe change being tested is a fix for the problem.

In accordance with another important aspect of the present invention,and referring to Appendix A generally, the events that occur not onlyresult in the generation of a 2 digit code, but the event is alsorecorded in the memory associated with the CPU 48. The operator of thevehicle has the capability of overriding a number of fault conditionsduring propulsion of the vehicle for a predetermined number of times,depending upon the particular condition. It should be understood thatthe occurrence of a fault condition during the propulsion mode ofoperation results in the CPU 48 generating a command to the maincontactors 74 and 76 which causes them to open, which results in thevehicle being stopped. Once it has stopped, the operator can operate theoverride switch to attempt to continue operation. If the vehicle is inthe retard mode where braking may be essential to preclude a runawaycondition from occurring, the processing means will not open contactors80 and 82, for to do so may cause such a runaway condition. The decaytime period also functions to define the period during which theoverride limit is effective.

The override is done by the operator by depressing a switch 95 that islocated in the cab of the vehicle. However, each fault has a limitconstraining the further overriding of the fault condition. Once thislimit has been reached, further overrides are disallowed, the vehicle isshut down and maintenance personnel must inspect the vehicle and eithercorrect the problem or perform a reset from the 2-digit display. Asshown in Appendix A, event 01, for example, which is for a low levelground fault, it can be reset up to four occurrences of the fault, butevent 02, relating to a high level ground fault, cannot be reset,because it is a dangerous fault condition.

The display 90 also has a connector 93 into which a portable test unit,preferably a portable laptop or smaller computer (not shown), can beconnected for the purpose of obtaining data and information from thememory of the CPU 48, including the displayed information that may havebeen removed from the display 90 in response to the reset switch 98operation. Such an operation only removes the codes from the display 90,and the information is still maintained in the memory of the CPU 48, andmay be accessed by the portable test unit if desired.

As previously described, the sampling is preferably performed every 0.01seconds, but can be adjusted preferably within the range of about 0.01seconds to 1 second by the operator. If the sampling is done moreinfrequently, there may be a need to gather data more often, and thesystem includes a switch 106 which enables a "snapshot" of gathered dataat each operation of the switch 106. This corresponds to the code 98shown in Appendix A.

The event values shown in Appendix A also include as acceptance limitvalue, which is an indication of the number of such events that can berecorded in memory before the oldest events of the particular type areoverwritten. A window limit is also provided, which is a higher prioritywriting of the same data and which is not overwritten by events writtenin the acceptance limit allocation of the memory.

While various embodiments of the present invention have been shown anddescribed, it should be understood that various alternatives,substitutions and equivalents can be used, and the present inventionshould only be limited by the claims and equivalents thereof.

Various features of the present invention are set forth in the followingclaims.

    __________________________________________________________________________    TWO-DIGIT DISPLAY PANEL CODES                                                 EVENT DESCRIPTION                                                                              EVENT RESTRICTIONS (IF ANY)                                                                      DETECTION INFORMATION                                                                          EVENT                    __________________________________________________________________________                                                         VALUES                   00 - Reset All   Not Displayed      Used to reset all events                  01 - Low Level Ground Fault                                                                    System Fault       A ground fault is detected if                                                                  Decay Time 1800                           In Accel: Shut down truck and turn                                                               age current to ground (truck                                                                   Lock Limit 5                              on SYSFLT light.   exceeds 114 ma. There is a                                                                     Accept Limit 20                           In Retard: Turn on SYSFLT light                                                                  second delay on shutdown. In                                                                   #Window Limit 5                           only.              following order, check for moisture                        All events are recorded in memory.                                                               in motors, grids and power cables,                                            motor flash, insulation failure in                                            power circuit, bad FB102 card.            02 - High Level Ground Fault                                                                   System Fault       A ground fault is detected if                                                                  Decay Time NA                                                age current to ground (truck                                                                   Lock Limit 1                                                 exceeds 140 ma. There is a                                                                     Accept Limit 1                                               second delay on shutdown.                                                                      #Window Limit 1                                              as No. 01.                                03 - Ground Test System Fault       Reset Fault - Tripped During                                                                   Decay Time                                                   ing.             Lock Limit                                                                    Accept Limit                                                                  #Window Limit            10 - GF Contactor                                                                              System Fault       GF contactor command and                                                                       Decay Time 3600                                              back don't agree. In the                                                                       Lock Limit 3                                                 order, check for welded                                                                        Accept Limit 10                                              blocked armature, defective coil                                                               #Window Limit 2                                              position sensor, loose connections                                            to coil or position sensor, mechani-                                          cal obstruction which prevents                                                smooth operation, bad FB104                                                   card.                                     11 - GFR relay   System Fault       GFR relay command and                                                                          Decay Time NA                                                don't agree. Same as No.                                                                       Lock Limit 1                                                                  Accept Limit 20                                                               #Window Limit 5          12 - MF Contactor                                                                              System Fault       MF contactor command and                                                                       Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          13 - P1 Contactor                                                                              System Fault       P1 contactor command and                                                                       Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          14 - P2 Contactor                                                                              System Fault       P2 contactor command and                                                                       Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          15 - RF1 Contacter                                                                             System Fault       RF1 contactor command and                                                                      Decay Time                                                   back don't agree. Same as No.                                                                  Lock Limit                                                   Series only.     Accept Limit                                                                  #Window Limit            16 - RF2 Contactor                                                                             System Fault       RF2 contactor command and                                                                      Decay Time                                                   back don't agree. Same as No.                                                                  Lock Limit                                                   Series only.     Accept Limit                                                                  #Window Limit            17 - RP1 Contactor                                                                             System Fault       RP1 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          18 - RP2 Contactor                                                                             System Fault       RP2 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          19 - RP3 Contactor                                                                             System Fault       RP3 contactor command and                                                                      Decay Time 3600                                              back don't agree. Some as No.                                                                  Look Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          20 - RP4 Contactor                                                                             System Fault       RP4 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          21 - RP5 Contactor                                                                             System Fault       RP5 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          22 - RP6 Contactor                                                                             System Fault       RP6 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          23 - RP7 Contactor                                                                             System Fault       RP7 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          24 - RP8 Contactor                                                                             System Fault       RP8 contactor command and                                                                      Decay Time 3600                                              back don't agree. Same as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          25 - RP9 Contactor                                                                             System Fault       RP9 contactor command and                                                                      Decay Time 3600                                              back don't agree. Some as No.                                                                  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          26 - Forward Coil                                                                              System Fault       Forward position of reverser                                                                   Decay Time 3600                                              mand and feedback don't                                                                        Lock Limit 3                                                 Same as No. 10.  Accept Limit 10                                                               #Window Limit 2          27 - Reverser Coil                                                                             System Fault       Reverse position of reverser                                                                   Decay Time 3600                                              mand and feedback don't                                                                        Lock Limit 3                                                 Same as No. 10.  Accept Limit 10                                                               #Window Limit 2          28 - Forward/Reverse Call                                                                      System Fault       Forward and reverse direction                                                                  Decay Time 3600                                              called for at the same                                                                         Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          29 - ERC Relay                      Reserved for Series                                                                            Decay Time                                                                    Lock Limit                                                                    Accept Limit                                                                  #Window Limit            30 - Digital/Analog Output Ex-                                                                 Record In Memory Only                                                                            Software error; bad FB101 or                                                                   Decay Time               ceeds 10 v or 1 ma                  card.            Lock Limit                                                                    Accept Limit                                                                  #Window Limit            31 - Analog Readback                                                                           Record In Memory Only                                                                            Same as No. 30.  Decay Time                                                                    Lock Limit                                                                    Accept Limit                                                                  #Window Limit            32 - Digital/Analog Input Exceeds                                                              Record In Memory Only                                                                            Same as No. 30.  Decay Time               Maximum                                              Lock Limit                                                                    Accept Limit                                                                  #Window Limit            33 - Frequency Input                                                                           Record In Memory Only                                                                            Some as No. 30.  Decay Time                                                                    Lock Limit                                                                    Accept Limit                                                                  #Window Limit            34 - Frequency Hardware                                                                        Record In Memory Only                                                                            Same as No. 30.  Decay Time                                                                    Lock Limit                                                                    Accept Limit                                                                  #Window Limit            35 - Analog A to D                                                                             Record In Memory Only                                                                            Same as No. 30. RAM                                                                            Decay Time                                                   Check            Lock Limit                                                                    Accept Limit                                                                  #Window Limit            37 - Startup (CPU) Fault                                                                       System Stop        May or may not inhibit                                                                         Decay Time,                                                  depending on the severity.                                                                     Lock Limit                                                   sub-codes (Table 6) with PTU                                                                   Accept Limit                                                 more detail. Check for bad                                                                     #Window Limit                                                card.                                     45 - Diode Fault System Fault       Ripple current in alternator                                                                   Decay Time NA                                                circuit exceeds a preset value                                                                 Lock Limit 1                                                 cates shorted diodes in main                                                                   Accept Limit 4                                               fier. Check diodes, wiring                                                                     #Window Limit 2                                              FDP and FL275 panel. Bed FDP,                                                 bad FB103 card.                           46 - Motor 1 Overcurrent                                                                       System Fault       Current in motor 1 armature                                                                    Decay Time 3600                                              ceeds limits for a preset time.                                                                Lock Limit 3                                                 is a function of being in retard                                                               Accept Limit 10                                              acceleration.    #Window Limit 2          47 - Motor 2 Overcurrent                                                                       System Fault       Current in motor 2 armature                                                                    Decay Time 3600                                              ceeds limits for a preset time.                                                                Lock Limit 3                                                 is a function of being in retard                                                               Accept Limit 10                                              acceleration.    #Window Limit 2          48 - Motor Field Fault                                                                         System Fault       Motor field current not in                                                                     Decay Time 3600                                              proportion with motor                                                                          Lock Limit 3                                                 current. Check for bad shunt,                                                                  Accept Limit 10                                              amp, wires, bad FB102                                                                          #Window Limit 2          49 - Motor Field Overcurrent                                                                   System Fault       Current in motor fields                                                                        Decay Time 3600                                              limits. Limit is a function of                                                                 Lock Limit 3                                                 in retard or acceleration.                                                                     Accept Limit 10                                                               #Window Limit 2          50 - Motor Stall System Fault (in Accel Only)                                                                     Motors stalled with motor                                                                      Decay Time 3600                                              above 1000 amps, inverse                                                                       Lock Limit 3                                                 function. Could be caused by                                                                   Accept Limit 10                                              loaded truck, grade or rolling                                                                 #Window Limit 2                                              tance too high. Check for bad                                                 speed sensors, shunts, iso amps,                                              wiring, bad FB102 card.                   51 - Motor Spin  System Fault       One motor stuck, the other                                                                     Decay Time 3600                                              ning for longer than 10                                                                        Lock Limit 3                                                 (preset delay). Same as No.                                                                    Accept Limit 10                                                               #Window Limit 2          52 - Alternator Tertiary Overcur-                                                              System Fault       Current in alternator field                                                                    Decay Time NA            rent                                windings exceeds limits for                                                                    Lock Limit 1                                                 preset time. Check for                                                                         Accept Limit 4                                               diodes or SCRs in AFSE.                                                                        #Window Limit 2                                              for low engine rpm.                       53 - Motor Tertiary Overcurrent                                                                System Fault       Current in motor field                                                                         Decay Time NA                                                windings exceeds limits for a                                                                  Lock Limit 1                                                 time. Check for shorted diodes                                                                 Accept Limit 4                                               SCRs in MFSE. Check for low                                                                    #Window Limit 2                                              gine rpm in Retard mode.                  54 - +15 Power   System Fault       Out Of Limit (±1 v) for 4                                                                   Decay Time 3600                                              Check for battery volts below 20                                                               Lock Limit 3                                                 excessive load on supply (iso                                                                  Accept Limit 10                                              or VMM), bad FB100 card.                                                                       #Window Limit 2          55 - -15 Power   System Fault       Out Of Limit (±1 v) for 4                                                                   Decay Time 3600                                              Same as No. 54.  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          56 - +19 Power   System Fault       Out Of Limit (±3 v) for 4                                                                   Decay Time 3600                                              Same as No. 54.  Lock Limit 3                                                                  Accept Limit 10                                                               #Window Limit 2          57 - Motor Polarity                                                                            System Fault       Motor 1 and Motor 2 opposite                                                                   Decay Time 3600                                              larity. Check for loose wiring                                                                 Lock Limit 3                                                 shunts, cabling to motors                                                                      Accept Limit 10                                              shunts, bad FB102 card.                                                                        #Window Limit 2          58 - Grid Failure                                                                              System Fault       Retard Grid Circuit Failure.                                                                   Decay Time                                                   for loose cabling to grids.                                                                    Lock Limit                                                   grids for foreign objects or                                                                   Accept Limit                                                 damage.          #Window Limit            59 - PTU Configuration                                                                         System Fault       PTU configuration inputs                                                                       Decay Time NA                                                inconsistent.    Lock Limit 1                                                                  Accept Limit 4                                                                #Window Limit 2          60 - On Trolley  System Fault       Unable to complete the                                                                         Decay Time NA                                                from diesel to trolley.                                                                        Lock Limit 1                                                 Not in use.      Accept Limit 4                                                                #Window Limit 2          61 - Off Trolley System Fault       Unable to complete the                                                                         Decay Time NA                                                from trolley to diesel.                                                                        Lock Limit 1                                                 Not in use.      Accept Limit 4                                                                #Window Limit 2          63 - Low Axle Box Pressure                                                                     If BPS does not pick up in 101 sec-                                                              Axle box air pressure not                                                                      Decay Time NA                             onds, turn on light and buzzer.                                                                  with engine above 1550                                                                         Lock Limit NA                                                Check for bad air ducts, open                                                                  Accept Limit 10                                              box door, bad axle box door                                                                    #Window Limit 0                                              kets, bad BPS switch, bad F8103                                               card.                                     64 - Motor 1 Over Temperature                                                                  Turn On Light.     Motor 1 is over 220° C.                                                temperature      Decay Time NA                                                limit. Could be caused by                                                                      Lock Limit NA                                                duty or lack of sufficient                                                                     Accept Limit 10                                              air.             #Window Limit 0          65 - Motor 2 Over Temperature                                                                  Turn On Light      Motor 2 is over 220° C.                                                temperature      Decay Time NA                                                limit. Could be caused by                                                                      Lock Limit NA                                                duty or lack of sufficient                                                                     Accept Limit 10                                              air.             #Window Limit 0          66 - Overspeed   Apply maximum retard level to re-                                                                Vehicle speed exceeds                                                                          Decay Timse NA                            duce speed below overspeed                                                                       limit.           Lock Limit NA                             point. Turn an light.               Accept Limit 50                                                               #Window Limit 0          67 - Speed Retard                                                                              Record In Memory Only                                                                            Vehicle speed exceeds retard                                                                   Decay Time NA                                                velope.          Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          68 - Retard Over Current                                                                       Record in Memory Only                                                                            Retard current level                                                                           Decay Time NA                                                Check for bad shunt, iso amp                                                                   Lock Limit NA                                                bad FB102 card.  Accept Limit 25                                                               #Window Limit 1          69 - Horsepower Low                                                                            Record In Memory Only                                                                            Engine is low on horsepower                                                                    Decay Limit NA                                                                Lock Limit NA                                                                 Accept Limit 25                                                               #Window Limit 1          70 - Horsepower Limit                                                                          Record In Memory Only                                                                            Engine horsepower limit is                                                                     Decay Time NA                                                ed.              Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          71 - Engine Overspeed                                                                          Record In Memory Only                                                                            Engine speed is exceeded.                                                                      Decay Time NA                                                                 Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          72 - Oil Pressure Warning                                                                      Record In Memory, Turn On ENG-                                                                   Engine oil pressure in                                                                         Decay Time NA                             MON Light.         zone. Could be caused by an                                                                    Lock Limit NA                                                gine problem, bed sensor,                                                                      Accept Limit 10                                              FB102 card.      #Window Limit 1          73 - Oil Pressure Shutdown                                                                     Record In Memory. Turn On ENG-                                                                   Engine oil pressure in                                                                         Decay Time NA                             MON Light.         zone. Same as No. 72.                                                                          Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          74 - Coolant Pressure Warning                                                                  Record In Memory. Turn On ENG-                                                                   Engine coolant pressure in                                                                     Decay Time NA                             MON Light.         zone. Same as No. 72.                                                                          Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          75 - Coolant Pressure Shutdown                                                                 Record In Memory, Turn On ENG-                                                                   Engine coolant pressure in                                                                     Decay Time NA                             MON Light.         down zone. Same as No.                                                                         Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          76 - Crankcase Overpressure                                                                    Record In Memory, Turn On ENG-                                                                   Engine crankcase overpressure.                                                                 Decay Time NA                             MON Light.         Same as No. 72.  Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          77 - Coolant Oventemperature                                                                   Record In Memory, Turn On EN-                                                                    Engine coolant temperature                                                                     Decay Time NA                             GOVERTEMP Light.   warning zone. Same as No.                                                                      Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          78 - Engine Service                                                                            Record In Memory. Turn On ENG-                                                                   Engine warning. Service                                                                        Decay Time NA                             MON Light.         (Detroit Diesels with DDEC                                                                     Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          79 - Engine Shutdown                                                                           Record In Memory, Turn On ENG-                                                                   Engine shutdown ASAP                                                                           Decay Time NA                             MON Light.         Diesels with DDEC only. It                                                                     Lock Limit NA                                                inhibit propulsion after a 15                                                                  Accept Limit 10                                              delay and will continue to inhibit                                                             #Window Limit 1                                              long as the DDEC Engine                                                       Shutdown light is lit.                    80 - Engine Speed Retard                                                                       Record In Memory   Engine Speed less than 1500                                                                    Decay Time NA                                                measured 4 seconds after high                                                                  Lock Limit NA                                                command when going into                                                                        Accept Limit 10                                              Check engine control and                                                                       #Window Limit 1          81 - Motor 1 Voltage Limit                                                                     Reduce alternator excitation such                                                                Motor 1 is over voltage                                                                        Decay Time NA                             that voltage limit is not exceeded. Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          82 - Motor 2 Voltage Limit                                                                     Reduce alternator excitation such                                                                Motor 2 is over voltage                                                                        Decay Time NA                             that voltage limit is not exceeded. Lock Limit NA                                                                 Accept Limit 10                                                               #Window Limit 1          83 - Alternator Field Current Lev-                                                             Record In Memory Only                                                                            Alternator field current is slow                                                               Decay Time NA            el                                  decay. Check for bad shunt,                                                                    Lock Limit NA                                                amp, bad FB102 card.                                                                           Accept Limit 10                                                               #Window Limit 1          90 - Battery Low Record In Memory Only                                                                            Battery volts low, less than 24                                                                Decay Time NA                                                for 4 seconds and the                                                                          Lock Limit NA                                                speed is greater than 600                                                                      Accept Limit 10                                              Check for bad battery charger                                                                  #Window Limit 1                                              bad battery.                              91 - Battery High                                                                              Record In Memory Only                                                                            Battery volts high, greater then                                                               Decay Time NA                                                volts for 4 seconds. Check for                                                                 Lock Limit NA                                                battery charger regulator.                                                                     Accept Limit 10                                                               #Window Limit 1          92 - Bad Engine Sensor                                                                         Record In Memory Only                                                                            Engine Sensor Output Outside                                                                   Decay Time                                                   Normal Range. Check for bad                                                                    Lock Limit                                                   sor wiring or bad sensor.                                                                      Accept Limit                                                                  #Window Limit            98 - Data Store                     Indicates that a data snap shot                                                                Decay Time NA                                                been initiated by manual                                                                       Lock Limit NA                                                                 Accept Limit 50                                                               #Window Limit 16         99 - Software                       Software problem. Reload                                                                       Decay Time                                                   ware, reconfigure truck. Check                                                                 Lock Limit                                                   bad FB101 card.  Accept Limit                                                                  #Window                  __________________________________________________________________________                                                         Limit                     NOTE:                                                                         The information listed under "EVENT VALUES" provides additional detail fo     each event, and is described as follows:                                      Decay Time = How long faults are held in memory (in seconds).                 Lock Limit = Maximum number of resets allowed.                                Acceptable Limit = Maximum number of events which can be recorded.            #Window Limit = Number of events with 51 windows.                        

What is claimed is:
 1. A control system for an electrical propulsionsystem for a wheeled vehicle adapted to haul a payload, the vehiclebeing equipped with a plurality of adjustable speed electric tractionmotors mechanically coupled in driving relation to separate wheels onthe vehicle, the vehicle having an internal combustion engine and anelectric generating means operatively connected to the engine and to thetraction motors and providing electric power at its output forenergizing the traction motors, the electric generating means being ofthe type which can vary the voltage and current of the electric powerprovided at its output responsive to control signals being appliedthereto and having a first predetermined operating temperature of acomponent thereof that correlates to a rating at which continuousoperation can occur without substantial risk of damage thereto, and amaximum predetermined operating temperature higher than the firstpredetermined operating temperature of the component during whichcontinuous operation would create a substantial risk of damage to theelectric generating means, said control system comprising:processingmeans including memory means for controlling the operation of theinternal combustion engine and the electric generating means; means formeasuring the ambient temperature of the environment in which thevehicle is operating and generating a signal indicative of said measuredambient temperature and applying the same to said processing means;means for measuring the output voltage of the electric generating meansand generating a signal indicative of said measured output voltage andapplying the same to said processing means; means for measuring theoutput current of the electric generating means and generating a signalindicative of said measured output current and applying the same to saidprocessing means; said processing means being adapted to generate thecontrol signals and apply the same to the electric generating means toincrease the electric power provided at its output above the continuousrating and to generate and apply the control signals to the electricgenerating means to return the same to the continuous rating responsiveto a calculated simulated temperature reaching the maximum predeterminedoperating temperature of the component of the electric generating means.2. A system as defined in claim 1 wherein said simulated temperature isa function of the measured ambient temperature, the measured outputvoltage, the measured output current and predetermined physicalcharacteristics of the electric generating means.
 3. A system as definedin claim 2 wherein said electric generating means is an alternatoradapted to convert the mechanical power of the engine to a three phasealternating current electrical output.
 4. A system as defined in claim 3wherein said component comprises a rotor of said alternator.
 5. A systemas defined in claim 4 wherein said predetermined physicalcharacteristics comprise at least the heat storage capacity of saidrotor of said alternator.
 6. A system as defined in claim 4 wherein saidpredetermined physical characteristics comprise at least the resistanceof said rotor of said alternator at a predetermined temperature.
 7. Asystem as defined in claim 4 wherein said predetermined physicalcharacteristics comprise at least the surface heat transfer coefficientof said rotor of said alternator.
 8. A system as defined in claim 7wherein said surface heat transfer coefficient varies in proportion tothe speed at which the engine operates, said system having a pluralityof coefficients stored in said memory means of said processing meanscorresponding to a plurality of preselected engine speeds.
 9. A systemas defined in claim 8 wherein three coefficients are stored in saidmemory means, said coefficients corresponding to a low idle speed, ahigh idle speed and a rated engine speed.
 10. A system as defined inclaim 1 wherein said processing means is adapted to generate saidcontrol signals on a periodic basis.
 11. A system as defined in claim 10wherein said processing means generates said control signalsapproximately every 5 seconds.
 12. A system as defined in claim 1wherein said electric generating means is adapted to vary the outputvoltage and output current to said traction motors to maintain aconstant horsepower rating responsive to said control signals, saidprocessing means being adapted to generate said control signals to saidelectric generating means to increase said output current and outputvoltage in proportion to maintain a constant horsepower rating whenoperating said electric generating means whereby the temperature of saidcomponent is above said first predetermined operating temperature.
 13. Asystem as defined in claim 2 wherein said processing means calculatessaid simulated temperature by executing the equation: ##EQU2## whereT=temperature rise of rotor (°C.),Δt=Time step, H=Surface heat transfercoefficient (Watts/C), C=Heat storage capacity (watt-sec./°C.),R=Resistance of rotor (ohms), I=RMS amps during Δt, and T_(amb) =Ambienttemperature (°C).
 14. An electrical propulsion system for a wheeledvehicle adapted to haul a payload, the vehicle having an internalcombustion engine for powering the vehicle, said system comprising:aplurality of adjustable speed electric traction motors mechanicallycoupled in driving relation to separate wheels on the vehicle, anelectric alternator operatively connected to the engine and to saidtraction motors and providing electric power at its output forenergizing said traction motors, said electric alternator being of thetype which has a rotor and an output and which can be controlled to varythe voltage and current of the electric power provided at its outputresponsive to control signals being applied thereto and having a firstpredetermined operating temperature of said rotor thereof thatcorrelates to a rating at which continuous operation can occur withoutsubstantial risk of damage thereto, and a maximum predeterminedoperating temperature higher than said first predetermined operatingtemperature of said rotor during which continuous operation would createa substantial risk of damage to said electric alternator, processingmeans including memory means for controlling the operation of theinternal combustion engine and said electric alternator; means formeasuring the ambient temperature of the environment in which thevehicle is operating and generating a signal indicative of said measuredambient temperature and applying the same to said processing means;means for measuring the output voltage of the electric alternator andgenerating a signal indicative of said measured output voltage andapplying the same to said processing means; means for measuring theoutput current of said electric alternator and generating a signalindicative of said measured output current and applying the same to saidprocessing means; said processing means being adapted to generate thecontrol signals and apply the same to said electric alternator toincrease the electric power provided at its output above the continuousrating and to generate and apply the control signals to said electricalternator to return the same to said continuous rating responsive to acalculated simulated temperature reaching the maximum predeterminedoperating temperature of said rotor of said electric alternator, saidsimulated temperature being a function of the measured ambienttemperature, the measured output voltage, the measured output currentand predetermined physical characteristics of said electric alternator.15. A control system for an electrical propulsion system for a wheeledvehicle adapted to haul a payload, the vehicle being equipped with aplurality of adjustable speed electric traction motors mechanicallycoupled in driving relation to separate wheels on the vehicle, thevehicle having an internal combustion engine and an electric generatingmeans operatively connected to the engine and to the traction motors andproviding electric power at its output for energizing the tractionmotors, the electric generating means being of the type which can varythe voltage and current of the electric power provided at its outputresponsive to control signals being applied thereto, the engine having apredetermined nominal horsepower rating, said control systemcomprising:processing means including memory means for controlling theoperation of the internal combustion engine and the electric generatingmeans; means for measuring the operating speed of the engine andgenerating a signal indicative of said measured speed and applying thesame to said processing means; said processing means being adapted togenerate the control signals and apply the same to the electricgenerating means to vary the electric power provided at its output andtherefore vary the load being applied on the engine, said processingmeans being adapted to operate in one of at least two horsepower loadingmodes, one of said modes being a manual mode whereby the electric powerprovided at the output of said electric generating means is set to apredetermined value corresponding to the nominal horsepower rating ofthe engine, the other of said modes being an automatic mode whereby theelectric power provided at the output of said electric generating meansis set at a predetermined nominal value, said processing means beingadapted to generate the control signals and apply the same to theelectric generating means to increase the electric power provided at theoutput thereof above said predetermined nominal value up to a maximumvariable level that is determined by said processing means receiving asignal from said measuring means indicative of said measured speeddropping below a predetermined speed.
 16. A system as defined in claim15 further comprising means for selecting one of said horsepower loadingmodes.
 17. A system as defined in claim 15 wherein the electricgenerating means comprises an electrical alternator and the internalcombustion engine comprises a diesel engine.
 18. A control system for anelectrical propulsion system for a wheeled vehicle adapted to haul apayload, the vehicle being equipped with a plurality of adjustable speedelectric traction motors mechanically coupled in driving relation toseparate wheels on the vehicle, the vehicle having an internalcombustion engine with a nominal horsepower rating and an electricgenerating means operatively connected to the engine and to the tractionmotors and providing electric power at its output for energizing thetraction motors, the electric generating means being of the type whichcan vary the voltage and current of the electric power provided at itsoutput responsive to control signals being applied thereto, the electricgenerating means having a nominal output power level that loads theengine at its nominal horsepower rating, said control systemcomprising:processing means including memory means for controlling theoperation of the internal combustion engine and the electric generatingmeans; means for measuring the operating speed of the engine andgenerating a signal indicative of said measured speed and applying thesame to said processing means; said processing means being adapted togenerate the control signals and apply the same to the electricgenerating means to vary the electric power provided at its output andtherefore vary the load being applied on the engine, said processingmeans being adapted to generate the control signals and apply the sameto the electric generating means to increase the electric power providedat the output thereof above said nominal output power level up to amaximum variable level that is determined by said processing meansreceiving the signal from said measuring means indicative of saidmeasured operating speed of the engine dropping below a predeterminedspeed.
 19. A system as defined in claim 18 wherein said processing meansis adapted to selectively operate in one of at least first and secondloading modes, said first mode being a manual mode whereby the electricpower provided at the output of said electric generating means is set tosaid nominal output power level, said second mode being an automaticmode whereby the electric power provided at the output of said electricgenerating means is set at said nominal output power level, saidprocessing means being adapted to generate the control signals and applythe same to the electric generating means to increase the electric powerprovided at the output thereof above said nominal output power level upto a maximum variable level that is determined by said processing meansreceiving the signal from said measuring means indicative of saidmeasured operating speed of the engine dropping below said predeterminedspeed.
 20. A method of operating an electrical propulsion system of awheeled vehicle adapted to haul a payload, the vehicle being equippedwith a plurality of adjustable speed electric traction motorsmechanically coupled in driving relation to separate wheels on thevehicle, the vehicle having an internal combustion engine with a nominalhorsepower rating, and an electric generating means operativelyconnected to the engine and to the traction motors and providingelectric power at its output for energizing the traction motors, theelectric generating means being of the type which can vary the voltageand current of the electric power provided at its output responsive tocontrol signals being applied thereto, the system having processingmeans for controlling the operation of the internal combustion engineand the electric generating means, said processing means being adaptedto generate the control signals and apply the same to the electricgenerating means to vary the electric power provided at its output andtherefore vary the load being applied on the engine, and means formeasuring the operating speed of the engine and generating a signalindicative of said measured speed and applying the same to saidprocessing means, said method comprising the steps of:generating thecontrol signals and applying the same to the electric generating meansto increase the load being applied on the engine; generating the controlsignals and applying the same to the electric generating means tomaintain the load being applied on the engine when the measuredoperating speed of the engine falls below a predetermined value.
 21. Amethod of operating an electrical propulsion system for a wheeledvehicle which is adapted to haul a payload, the vehicle being equippedwith a plurality of adjustable speed electric traction motorsmechanically coupled in driving relation to separate wheels on thevehicle, the vehicle having a diesel engine with a nominal horsepowerrating, and an electric alternator operatively connected to the engineand to the traction motors and providing electric power at its outputfor energizing the traction motors, the electric alternator being of thetype which can vary the voltage and current of the electric powerprovided at its output responsive to control signals being appliedthereto, the system having processing means for controlling theoperation of the diesel engine and the electric alternator, saidprocessing means being adapted to generate the control signals and applythe same to the electric alternator to vary the electric power providedat its output and therefore vary the load being applied on the engine,and means for measuring the operating speed of the engine and generatinga signal indicative of said measured speed and applying the same to saidprocessing means, said method comprising the steps of:generating thecontrol signals and applying the same to the electric alternator tooperate the alternator at a predetermined alternator output that causesthe engine to operate near its nominal horsepower rating; measuring theoperating speed of the engine and generating the control signals andapplying the same to the electric alternator to increase the load beingapplied to the engine until the measured operating speed of the enginefalls below a predetermined value; and, generating the control signalsand applying the same to the electric alternator to operate thealternator at an alternator output level that causes the engine tooperate at least at said predetermined value of operating speed.
 22. Acontrol system for an electrical propulsion system for a wheeled vehicleadapted to haul a payload, the vehicle being equipped with a pluralityof adjustable speed electric traction motors mechanically coupled indriving relation to separate wheels on the vehicle, the vehicle havingan internal combustion engine and an electric generating meansoperatively connected to the engine and to the traction motors andproviding electric power at its output for energizing the tractionmotors, the electric generating means being of the type which can varythe voltage and current of the electric power provided at its outputresponsive to control signals being applied thereto and having a firstpredetermined operating temperature of a component thereof thatcorrelates to a rating at which continuous operation can occur withoutsubstantial risk of damage thereto, and a maximum predeterminedoperating temperature higher than the first predetermined operatingtemperature of the component during which continuous operation wouldcreate a substantial risk of damage to the electric generating means,said control system comprising:processing means including memory meansfor controlling the operation of the internal combustion engine and theelectric generating means, said processing means including time andcalendar means for providing time and date stamps for selective signalsthat are received by said processing means; means for measuringpreselected electrical parameters of the electric generating means andgenerating electrical signals respectively indicative of said measuredelectrical parameters and applying the same to said processing means;means for measuring preselected mechanical and operating parameters ofthe engine and generating electrical signals respectively indicative ofsaid measured mechanical and operating parameters and applying the sameto said processing means; means for measuring preselected mechanical andoperating parameters of the vehicle and generating electrical signalsrespectively indicative of said measured mechanical and operatingparameters and applying the same to said processing means; saidprocessing means being adapted to receive said electrical signals fromeach of said measuring means and write selective historical data in saidmemory means relating to the history of operation of the vehicle, theelectric generating means and the engine.
 23. A system as defined inclaim 22 wherein said processing means writes said historical data insaid memory means and maintains said data for predetermined periods oftime.
 24. A system as defined in claim 23 wherein said historical dataprovides a daily record of selective mechanical, electrical andoperating parameters.
 25. A system as defined in claim 23 wherein saidhistorical data provides a record of selective mechanical, electricaland operating parameters for a predetermined number of quarters of ayear.
 26. A system as defined in claim 23 wherein said historical dataincludes data indicating the time duration of selected operatingparameters of the vehicle.
 27. A system as defined in claim 23 whereinsaid historical data includes data comprising the cumulative total ofselected operating parameters.
 28. A system as defined in claim 26wherein said historical data includes data that indicates the timeduration of operation of the engine, operation of the vehicle, operationof the electric generating means, and operation of the vehicle above apredetermined speed.
 29. A system as defined in claim 22 includingdisplay means operatively connected to said processing means, saiddisplay means having a multiple digit readout, said processing meansbeing adapted to generate electrical signals to said display means forproviding selected visual indications of a plurality of operationalparameters relating to the vehicle and said system.
 30. A system asdefined in claim 29 wherein said display means is adapted to display aplurality of two digit codes, each of which indicates a status conditionrelating to the operation of the vehicle and the system.
 31. A system asdefined in claim 30 wherein a description of troubleshooting techniquesis associated with each of said plurality of two digit codes.
 32. Asystem as defined in claim 31 wherein said description oftroubleshooting techniques is accessed via an operator input meansassociated with said display means.
 33. A control system for anelectrical propulsion system for a wheeled vehicle adapted to haul apayload, the vehicle being equipped with a plurality of adjustable speedelectric traction motors mechanically coupled in driving relation toseparate wheels on the vehicle, the vehicle having an internalcombustion engine and an electric generating means operatively connectedto the engine and to the traction motors and providing electric power atits output for energizing the traction motors, said control systemcomprising:processing means including memory means for controlling theoperation of the internal combustion engine and the electric generatingmeans, said processing means including time and calendar means forproviding time and date stamps for selective signals that are receivedby said processing means, and to determine preselected fault conditionsin response to receiving signals indicative of preselected mechanicaland electrical parameters that are outside of predetermined limits;means for measuring preselected electrical parameters of the electricgenerating means and generating electrical signals respectivelyindicative of said measured electrical parameters and applying the sameto said processing means; means for measuring preselected mechanical andoperating parameters of the engine and generating electrical signalsrespectively indicative of said measured mechanical and operatingparameters and applying the same to said processing means; means formeasuring preselected mechanical and operating parameters of the vehicleand generating electrical signals respectively indicative of saidmeasured mechanical and operating parameters and applying the same tosaid processing means; override switch means operatively connected tosaid processing means, and adapted to override a fault conditionresponsive to actuation thereof in the absence of an inhibitingcondition being established by said processing means; said processingmeans being adapted to receive said electrical signals from each of saidmeasuring means and determine a fault condition and write dataindicative of said fault condition in said memory means, said processingmeans stopping the vehicle in response to the fault condition beingdetermined.
 34. A system as defined in claim 33 further includingdisplay means operatively connected to said processing means, saiddisplay means having a multiple digital readout, said processing meansbeing adapted to generate electrical signals to said display means forproviding selected visual indications of a plurality of operationalparameters relating to the vehicle and said system, includingpreselected fault conditions.
 35. A system as defined in claim 34wherein said display means comprises at least one logic screen forproviding troubleshooting aid.
 36. A system as defined in claim 35wherein said at least one logic screen for providing troubleshooting aidcomprises two logic screens.
 37. A system as defined in claim 35 whereinsaid at least one logic screen contains ladder diagrams to allow adetermination of which signal is preventing the control system fromachieving an acceleration or a retard state.
 38. A system as defined inclaim 37 wherein said ladder diagrams comprise operator inputs andpropulsion system feedbacks.
 39. A system as defined in claim 33 whereinsaid processing means selectively includes a predetermined overridelimit for preselected fault conditions, said processing means generatingsaid inhibiting condition in response to said limit being reached.
 40. Asystem as defined in claim 34 wherein said display means includes areset means which when actuated, clears said visual indicationstherefrom, said electrical signals of said operational parameters andsaid preselected fault conditions being written in said memory means ofsaid processing means.
 41. A system as defined in claim 33 wherein saidprocessing means includes means for establishing a predetermined rate atwhich said processing means writes into said memory means the electricalsignals generated from each of said measuring means, said predeterminedrate being adjustable.
 42. A system as defined in claim 33 furtherincluding a snapshot switching means operatively connected to saidprocessing means, said snapshot switching means being adapted to writeinto said memory means the electrical signals generated from each ofsaid measuring means in response to actuation of said snapshot switchingmeans.